| Abstract: | The growth of the foodborne pathogen Listeria monocytogenes can be controlled by nisin, an antimicrobial peptide. A spontaneous mutant of L. monocytogenes shows both resistance to nisin and increased acid sensitivity compared to the wild type. Changes in the cell membrane correlated with nisin resistance, but the mechanism for acid sensitivity appears unrelated. When hydrochloric or lactic acid is added to cultures, intracellular ATP levels drop significantly in the mutant (P < 0.01) compared to the results seen with the wild type. Characterization of the F0F1 ATPase, which hydrolyzes ATP to pump protons from the cell cytoplasm, shows that the enzyme is more active in the mutant than in the wild type. These data support a model in which the increased activity of the mutant ATPase upon acid addition depletes the cells' supply of ATP, resulting in cell death. |
